Exploited CVEs / Cisco / CVE-2023-20109
CVE-2023-20109
Cisco IOS and IOS XE Group Encrypted Transport VPN Out-of-Bounds Write Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted. Federal agencies were required to remediate by 2023-10-31 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: Cisco Security Advisories (PSIRT), linked below.
Actively exploited Cisco IOS and IOS XE vulnerability, Medium severity, CVSS 6.6. Added to the CISA KEV catalog 2023-10-10.
Risk summary
Updated July 27, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
Senserva AI Opinion for CVE-2023-20109
Exploiting this Cisco IOS and IOS XE flaw in the Group Encrypted Transport VPN feature requires the attacker to already hold administrative control of a group member or key server, which is why EPSS sits at just 2% despite a CISA KEV listing. It is an insider-or-post-compromise tool: an out-of-bounds write that turns existing admin access into code execution on VPN infrastructure. The Medium Severity rating (CVSS 6.6) understates how useful that is to an attacker consolidating control.
Do this: Patch GET VPN key servers and group members, and review who holds administrative access to them.
AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2023-20109
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for CVE-2023-20109
Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.
CISA required action
Federal (BOD 22-01) remediation due date: 2023-10-31 (past due).
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Official fix for CVE-2023-20109
The authoritative fix and affected-version list are published by the vendor. Find the IOS and IOS XE advisory on Cisco Security Advisories (PSIRT).
Common questions about CVE-2023-20109
Is CVE-2023-20109 actively exploited?
Yes. CVE-2023-20109 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2023-10-10, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 2.3%.
What is the CISA deadline and required action for CVE-2023-20109?
CISA set the federal (BOD 22-01) remediation due date at 2023-10-31, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
What fixes CVE-2023-20109?
The authoritative fix is in the vendor advisory: see Cisco Security Advisories (PSIRT) for the patched IOS and IOS XE versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.
Can I ask my own AI about CVE-2023-20109?
Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2023-20109's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).
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